Examples of an imaging module including a lens, an imaging element, and a substrate include those disclosed in PTL 1 and PTL 2.
The imaging module disclosed in PTL 1 includes a roughly box lid-shaped holder for an imaging element. On a front side of the holder, an opening into which a translucent member such as glass or a filter is attached is formed and on a rear (opening) side thereof, an imaging element is attached. Between the translucent member and the imaging element in the holder, rectangular frame-shaped rubber packing is held in a compressed manner. More specifically, a rectangular ring-shaped light shielding rib is provided in a protruded manner on an outer peripheral side of the rubber packing and a notched rectangular ring-shaped pressing rib is provided in a protruded manner on an inner peripheral side of the light shielding rib in such a manner that the rubber packing has both of a light shielding function and a holding function thereof. Protruded leading ends of the light shielding rib and the pressing rib are pressed against the imaging element.
The imaging module disclosed in PTL 2 includes a stepped short-cylindrical pressing member arranged on a substrate in such a manner as to surround an imaging element mounted on the substrate, and an O-ring (sealing member) installed between a flange part, which is provided in a lower outer periphery of the pressing member, and the substrate. The O-ring is pressed against the substrate by the pressing member, whereby air-tightness (and light-shielding property) in the pressing member (space between translucent member and substrate) is secured.
On the other hand, recently, it is becoming popular to employ a stereo camera, which includes a pair of right and left imaging modules described above, as a vehicle driving support system to support safe driving of a car (see, for example, PTL 3).
The stereo camera calculates a distance to an object by triangulation with a pair of images acquired from the pair of right and left imaging modules and recognizes the object.
Specifically, in an environment in a vehicle, it is necessary to perform measurement of a distance to a distant object and recognition thereof accurately and securely since there is an application request for, for example, detecting a leading vehicle, a person, or an obstacle and dealing therewith previously and safely.
Moreover, in a case of using the stereo camera in the vehicle driving support system or the like, high reliability is required in addition to downsizing and lowering a price.
In the stereo camera, special LSI to perform processing of specifying pixel positions of feature points, which are common in a pair of images, in pixel information included in the images and of calculating the number of pixels deviated between the feature points in the pair of pictures (hereinafter, referred to as parallax) is generally included.
For the principle, it is preferable that there is no deviation between the pair of images other than the parallax. Thus, a structure to perform adjustment accurately in such a manner that deviation in an optical characteristic or signal characteristic is not generated and to keep the accuracy is necessary for each imaging module.
Also, in order to improve performance of detecting a leading vehicle or the like, it is necessary to accurately calculate feature points common in the pair of images. Thus, it is preferable that luminance values of feature points are the same in a reference imaging module and the other imaging module.
Thus, it is preferable that extraneous light other than signal light that becomes incident through a lens does not become incident through a place other than the lens.